The designers’intent for Call of Duty: Modern Warfare 3 was to allow the player to experience cool scripted “hero moments” during the single player campaign: time briefly slows down for everybody except for the player, who can take down multiple targets. User testing was employed to test these hero moments: a problem was detected in the mission “Hunter Killer”, when the player is escaping a sinking submarine on a watercraft and a patrol boat filled with enemy soldiers appears in pursuit. In the mind of the designers, the correct way to take on this particular hero moment was not shooting at the soldiers (there is not enough time to kill all three soldiers during the slow-mo), but instead aiming at some mines on the boat in order to make everything blow up in just one perfectly-timed move. However, during testing sessions players were just ignoring the mines and targeting the soldiers instead. In the end, players suffered multiple deaths without understanding what was wrong with their course of action. In order to fix this bad game experience, the designers decided to add a line of dialog: a fellow soldier would shout “Shoot the Mines!” to the player. Moreover, another fix was implemented: had the player ignored the mines, the boat would blow up by itself.
Schnurr, C. (2013). Pragmatic, Integrated, Scrappy-Fighty: User-Testing @Activision. Proceedings of the Games User Research Summit 2013. Retrieved here: http://player.vimeo.com/video/63870800 (Games User Research Summit Video Presentation)